There are venue codes and meeting codes and which is which can be different depending upon which file you are looking at.
For the last few months there has been errors on some of them probably due to Covid-19 leading to cessation of meetings that were scheduled and later restarted.
If you want venue codes to create bet strings best to use the daily race list file as it has less errors for the individual day and is up to date. eg http://www.tabinfo.com.au/racetabroot/racelists/default.aspx
However before the errors started it was more convenient to use a page that gave the venue codes for a month or two in advance rather than just a day found on http://www.tabinfo.com.au/calendar/racingcalendar.pdf?_ga=2.228968988.1004845410.1610428999-1389445039.1608149009
Now meeting codes are for race type normally be it horse greyhound or harness.
There are other calender pages which use the term meeting or schudule which use some of the codes in the above format but have a different meaning.
It can be confusing if looking at these pages for the first time.
The errors can cost you money so it pays to know what you are looking at. There were very few errors before Covid-19.
Most punters are blissfully ignorant of such things..... possibly the same ones that struggle to make a profit....
ps on days that have a large number of meetings venue codes and meeting codes can be merged or mixed up eg a race meeting may get a harness code eg TH instead of TR say when a TR has already been used for something else. This too can cost you money if you don't check; especially if you think you are betting into a 20g pool when in fact you are betting into a $300 pool only at some virtually unknown meeting that gets hardly any turnover on the TAB eg a picnic meet.